Definition of extensor in English:


(also extensor muscle)


  • A muscle whose contraction extends or straightens a limb or other part of the body.

    Often contrasted with flexor
    • ‘Then, when you've completed the movement, the flexor relaxes and the extensor contracts to extend or straighten the limb at the same joint.’
    • ‘The limb is supplied with a single extensor muscle and a single flexor, all other joints are considered rigid, and the objective of the CNS is to maintain the position of the limb.’
    • ‘Flexion force applied against long finger (third digit) extension distal to the proximal interphalangeal joint may provoke pain over the extensor muscle mass in the proximal forearm.’
    • ‘To offset well-established volume/area relationships limiting muscle force, larger animals walk on extended limbs and show allometric increases in extensor muscle lever arm lengths.’
    • ‘The anterior compartment flexor muscles of the arm are innervated by the musculocutaneous nerve, and the large posterior compartment extensor muscle is innervated by the radial nerve.’


Early 18th century: from late Latin, from extens- ‘stretched out’, from the verb extendere (see extend).